I shall attempt to study the ionophoric system responsible for Ca ions - release from skeletal muscle sarcoplasmic reticulum (SR). There exists in the literature almost no data at all on the nature of the Ca ions - release mechanism, but it is a reasonable hypothesis that it is a voltage-gated Ca ions channel which opens in response to a change in voltage across the SR membrane. I have searched for such a channel by causing the fusion of isolated SR vesicles with an artificial planar bilayer, and subsequently measuring the resulting conductance characteristics of the bilayer. In this way, a voltage-dependent, cation-selective ionophore has been observed. It is the main purpose of this proposal to study the electrical properties of this ionophore, including the Ca ions-specificity, kinetics, voltage-dependence, and inhibitor-sensitivity, in hopes of deducing its role in the physiological function of sarcoplasmic reticulum. Further work is also planned to fractionate the SR membranes and to discover whether the ionophore is truly associated with the SR or with the T-tubule membranes which contaminate the SR preparations. Finally, initial work will be performed on the isolation and reconstitution of the ionophore, as a first step towards purification and chemical characterization of the system.